His great-grandfather was India's first prime minister. His grandmother was the country's first – and thus far only – woman leader. And his father was the nation's youngest leader.

But yesterday Rahul Gandhi, the flag-bearer of the Nehru-Gandhi dynasty that has ruled the world's largest democracy for most of its 65 years of independence, was forced to accept responsibility for a humiliating defeat as his Congress Party was trounced in state elections that many saw as a referendum on him as a future leader.

The 41-year-old politician had placed himself front and centre of the Congress's attempt to rejuvenate itself after a series of high-profile scandals , especially in the country's largest and politically most important state, Uttar Pradesh (UP). But last night he had few options other than shouldering the blame after things went disastrously wrong at the polls.

"I accept responsibility for the fact that we did not perform well," he said. "After all, I was the main campaigner... the Congress Party fought well, but the result is not good." He delivered the remarks while standing outside the official Delhi residence of his mother, Sonia Gandhi, who is president of the party. The Italian-born Ms Gandhi turned down the prime minister's post when the Congress came to power in Delhi in 2004. "I promised to the people of UP that I will be seen with the poor, on the roads and fields," Mr Gandhi said. "My work will continue. My efforts will be to re-erect the Congress in UP."

On this most disappointing of days for the Congress, it was difficult not to notice the visual details that jarred. Mr Gandhi was unshaven and dressed in a simple white cotton shirt. When he had finished addressing the media, he walked into the consolatory embrace of his sister, Priyanka. And yet they both failed. His attempt to market himself as a champion of the down-trodden, someone willing to spend a night in the hut of a Dalit, or "untouchable", did not resonate sufficiently in a state where many of the health and nutrition indicators are no better than in sub-Saharan Africa.

Likewise, for all the hype within the Indian media about the purported "star power" of the Gandhi family, especially Priyanka, the Congress was badly beaten in those specific areas of UP where Mr Gandhi and his mother hold seats in the national parliament and where his sister vigorously campaigned on his behalf.

No one can accuse Mr Gandhi of not trying hard enough. During the election campaign, he spoke at more than 200 rallies, hurling himself into a frenetic schedule as he toured the state by helicopter. Valerian Rodrigues, a professor of political science of Delhi's Jawaharlal Nehru University, said he believed the result in UP and elsewhere – the Congress also lost in Goa and Punjab and the outcome was unclear in Uttarakhand – was the result of disillusionment with the national government rather than Mr Gandhi himself. Allegations of corruption, political deadlock and an apparent lack of direction appear to have angered voters. "It is a statement about governance," Professor Rodrigues said. "The Congress is not an impressive party."

There is little doubt that the result is also a body blow to the Prime Minister, Manmohan Singh, already seen as stumbling, two years away from the next general election. A decent result in UP would have boosted the government's ability to press ahead with reforms. As it is, the result has raised questions about the party's mandate.

In UP, Mr Gandhi had set out to see the incumbent chief minister, Mayawati, who draws her supporters from among the poorest sections of society, roundly defeated. That happened, but it was the rival socialist Samajwadi Party (SP) that stepped in to secure a simple majority in the state assembly.

While Congress did manage to increase its share of the overall vote, it only managed to increase its tally of seats in the UP assembly from 22 to 38.